Active-matrix liquid crystal display device and method for compensating for defective display lines

ABSTRACT

In a liquid crystal display device, auxiliary lines are formed under pixel electrodes so as to be parallel to signal or scanning lines. The auxiliary lines are connected to the signal or scanning lines at one point for each pixel. This permits a voltage to be applied to a signal or scanning line if a disconnection defect occurs in the signal or scanning line. The auxiliary line is connected to the signal or scanning line at opposite sides of the defect to form a circuit around the defect. Moreover, if a leakage defect occurs at a crossing point between the scanning line and the signal line, the signal or scanning line may be cut off at both sides of the scanning or signal line, and the auxiliary line forms a circuit that avoids the line leak. Thus, a voltage may be applied to the signal or scanning line by the auxiliary line.

This application is a division of Ser. No. 08/700,172, filed Aug. 20,1996, now U.S. Pat. No. 6,175,393.

RELATED APPLICATIONS

This application is related to the following commonly assignedco-pending applications: Ser. No. 08/695,632, filed Aug. 12, 1996, nowU.S. Pat. No. 5,052,162; Ser. No. 08/712,978, filed Sep. 12, 1996, nowU.S. Pat. No. 5,877,830; Ser. No. 08/697,277, filed Aug. 27, 1996; Ser.No. 08/705,759, filed Aug. 30, 1996, now U.S. Pat. No. 5,831,708; andSer. No. 08/725,663, filed Oct. 1, 1996, now U.S. Pat. No. 5,771,083.

FIELD OF THE INVENTION

The present invention relates to a display device for displaying byapplying a drive signal to a display-use pixel electrode through aswitching element, more particularly relates to a matrix-type liquidcrystal display device, which permits a high density display bydisposing pixel electrodes in a matrix form, and also relates to amethod of compensating for a defective pixel electrode in such displaydevice.

BACKGROUND OF THE INVENTION

A conventional display device such as a liquid crystal display device, aplasma display device, etc., includes a plurality of pixel electrodesdisposed in a matrix form, counter electrodes facing these pixelelectrodes, and a display medium (liquid crystal, plasma, etc.,) sealedbetween the pixel electrodes and the counter electrodes. The describeddisplay device selectively applies a voltage to the pixel electrodes toform a display pattern on a screen. Further, by applying a voltagebetween the selected pixel electrode and the counter electrode, thebrightness of the display medium is optically modulated by the displaydata to visualize the display pattern.

For the method of driving the pixel electrodes, a so-calledactive-matrix driving system is known wherein switching elements areconnected to respective pixel electrodes disposed in a matrix form andthe pixel electrodes are respectively driven by the switching elements.For the switching element, a TFT (thin-film transistor), and an MIM(metal-insulator-metal) element, etc., are generally known. On the otherhand, the pixel electrodes are typically formed on the substrate in thesame layer as signal lines, scanning lines (bus lines) in such a mannerthat they do not contact the signal lines or the scanning lines.

Additionally, the technique of forming pixel electrodes on a differentlayer from the bus lines by disposing the pixel electrodes on aninsulting film is proposed (Japanese Laid-Open Patent Application No.156025/1986 (Tokukaisho 61-156025). In the described arrangement, as thepixel electrodes and the bus lines are formed on different layers, anincreased area of the pixel electrodes (aperture ratio) can be achieved.

The liquid crystal display device adopting the matrix-type substratealways faces a problem of a disconnection of wire due to a defectgenerated in the manufacturing process. In order to suppress thegeneration of such disconnection defect, the active-matrix type liquidcrystal display device which adopts double bus lines has been proposed(SID '95 DIGEST of TECHNICAL PAPERS 4: AMLCDs 4.3; “High-Aperture andFault-Tolerant Pixel Structure for TFT-LCDs”).

As shown in FIG. 14, the described active-matrix type liquid crystaldisplay device is arranged such that two scanning lines 52 and 52′ areformed for each pixel electrode 5l, and the scanning lines 52 and 52′are short-circuited by short-circuit lines 54 formed along signal lines53 on both sides of the pixel electrode 51. The short-circuit lines 54are superimposed on the pixel electrode 51 via an insulating film (notshown), and an overlapped portion functions as an auxiliary capacitance.In the described arrangement, as a TFT 55 is driven by the two scanninglines 52 and 52′, even if a disconnection occurred in one of thescanning lines 52 and 52′, an application of the gate voltage to the TFT55 can be ensured through the short-circuit lines 54.

In general, in order to prevent light from leaking through a gap formedbetween the pixels, a light-shielding pattern is formed on the side ofthe counter electrodes. In the described arrangement, however, the pixelelectrode 51 and the short-circuit lines 54 are superimposed in adirection perpendicular to the substrate. Therefore, the short-circuitlines 54 form a part of the light-shielding pattern.

The arrangement where the pixel electrode and the signal line aresuperimposed via the insulating film will be explained.

In the arrangement shown in FIG. 15, peripheral portions on both sidesof the pixel electrodes 51 are superimposed on the scanning lines 52 andthe signal lines 53. As shown also in FIG. 16, at a central portionbelow the pixel electrode 51, formed is an auxiliary capacitanceelectrode (hereinafter referred to as Cs electrode) 56. The Cs electrode56 is formed on a gate-insulating film 57 used in common with the TFT 55(see FIG. 15). The Cs electrode 56 is in contact with a contact portion51 a of the pixel electrode 51.

On a substrate 58 made of glass, formed is an auxiliary capacitance line59. The gate insulating film 57 is formed so as to cover the auxiliarycapacitance line 59. On both sides of the Cs electrode 56 on the gateinsulating substrate 57, lower signal lines 60 are formed, and further,signal lines 53 are formed thereon. The lower signal lines 60 and thesignal lines 53 are covered with an insulating substrate 61.

In the described arrangement, as the insulating film 61 is formedbetween the pixel electrode 51 and the signal lines 53, an increasedarea of the pixel electrode 51 can be obtained irrespectively of thedisposed positions of the signal lines 53.

The arrangement shown in FIG. 17 includes the Cs electrode 56 having thesame structure as that of the aforementioned arrangement of FIG. 15,except that the Cs electrode 56 is connected to a drain electrode 62through a connection line 63. The arrangements shown in FIG. 15 and,FIG. 17 both have the Cs-on-Common structure wherein an auxiliary linecapacitance is formed by disposing the Cs electrode 56 on the commonauxiliary capacitance line 59 which is used in common among all thepixels.

On the other hand, the arrangement shown in FIG. 18 has the Cs-on-Gatestructure wherein an auxiliary capacitance is formed by disposing the Cselectrode 56 on the scanning line 52 of an adjacent pixel. In thisarrangement, the Cs electrode 56 is connected to a contact portion 51 bof the pixel electrode 51.

In the arrangement shown in FIG. 19, the Cs electrode 56 is connected tothe drain electrode 62 through the connection line 63.

With a demand for higher definition and higher aperture ratio, there isa tendency of reducing the width of the bus line while increasing thenumber of the bus-line crossing parts, which increases a disconnectionof a bus-line or a leakage at a portion where the bus-lines are crossed.Furthermore, such disconnection of bus-line, or the leakage at thecrossing point causes a problem that a voltage cannot be appliedproperly to the pixel electrode connected to the disconnected bus line.Therefore, the portion where the voltage is not applied appears as aline-shaped defect on the display screen. In the display element, suchline-shaped defect is a serious problem, and a display device havingsuch line-shaped defect is considered as an inferior good. Further, anincrease in such inferior goods would lower the yield of the displaydevice, thereby increasing a manufacturing cost.

Furthermore, when the described arrangement of adopting the double busline is applied to the general arrangement where the pixel electrode andthe bus line are formed in the same layer, as the pixel electrode isformed in the same layer as the bus line, an increased area of the pixelelectrode cannot be obtained, thereby hindering an improvement of theaperture ratio. Although a small improvement in aperture ratio can beachieved by reducing an interval between the wires; this would causesthe problem that a leakage between the wires is likely to occur.

In the arrangements shown in FIG. 15 through FIG. 19, it is permitted toarrange such that the pixel electrode 51 and the data electrodes 53 aresuperimposed. However, the capacitance between the pixel electrode 51and the signal line 53 cannot be made smaller due to the insulating film61 formed therebetween. Therefore, the problem of generating crosstalkdue to the capacitance, which would lower the display quality remainsunsolved.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an active-matrix typeliquid crystal display device whose structure permits a generation of aline-shaped defect to be prevented and an improved aperture ratio to beattained with ease.

In order to fulfill the above object, an active-matrix type liquidcrystal display device in accordance with the present invention whichincludes a plurality of scanning lines formed on a substrate; aplurality of signal lines formed so as to cross the scanning lines atright angle; a pixel electrode formed in a region surrounded by adjacentscanning lines and adjacent signal lines; and a switching element forswitching ON/OFF an application of a signal voltage to the pixelelectrode through the signal line by a scanning voltage to be applied tothe scanning line is characterized by further including the followingmeans.

Namely, the first active-matrix type liquid crystal display deviceincludes auxiliary lines formed in the same layer as the signal lines.Each auxiliary line short-circuits two portions of the signal line forapplying a signal voltage to corresponding two pixel electrodes whichare adjacent to one another along the signal lines.

The second active-matrix type liquid crystal display device is arrangedso as to include auxiliary lines formed in the same layer as thescanning lines. Each auxiliary line short-circuits two portions of thescanning line for applying a scanning voltage to corresponding two pixelelectrodes which are adjacent to one another along the scanning line.

According to the first active matrix-type liquid crystal display device,two portions of the signal line are short-circuited by the auxiliaryline. Therefore, when a disconnection defect occurred in the signalline, a signal voltage would be applied to the signal line through theauxiliary line so as to make a circuit around to avoid the disconnectedportion. This feature offers a particular effect that even if adisconnection defect occurred between a certain pixel electrode and anext pixel electrode, the signal voltage can be kept applying to thepixel electrode.

Similarly, in the second active-matrix type liquid crystal displaydevice, when a disconnection defect occurred in the scanning line, ascanning voltage is applied to the scanning line so as to make a circuitaround to avoid the disconnected portion. Therefore, the scanningvoltage can be kept applying to the pixel electrode.

As a result, a generation of a line-shaped defect is prevented, and goodproducts can be obtained at significantly improved yield. Here, thefollowing problem possibly occurs: That is, a signal line which startsbeing disconnected is finally disconnected after the active-matrix typeliquid crystal display device is delivered to the user. The describedactive-matrix type liquid crystal displays of the present inventionprovide the solution to the described problems and permits a displayquality to be ensured even in the described situation. Therefore, anactive-matrix type liquid crystal display device permits a reduction inmanufacturing cost while improving a reliability.

As a preferred form of the first or second active matrix-type liquidcrystal display device, it may be arranged such that each auxiliary lineis connected to a single signal line or a single scanning line at oneportion at a predetermined interval from the crossing point between thesignal line and the scanning line per each pixel region.

The conventional arrangement where the auxiliary line is connected tothe signal line or the scanning line at a plurality of portions formedat different intervals from the crossing point between the signal lineand the scanning line per pixel region has such a drawback that thesignal line or the scanning line between the connecting portions willnot be short-circuited to the signal line or the scanning linecorresponding to the adjacent pixel electrode. In contrast, thedescribed arrangement of the present invention eliminates the describedproblem, i.e., the defective portion where the signal line or thescanning line is not short-circuited by the auxiliary lines byspecifying the connecting portion between the auxiliary line and thesignal line or the scanning line.

The auxiliary line of the present invention is arranged so as to have aminimum length required for applying a signal voltage or the scanningvoltage in replace of the signal line or the scanning line at anoccurrence of disconnection defect. Therefore, even if a material of alarge specific resistance, such as ITO, etc., is adopted for theauxiliary line, an overall increase in resistance of the wires can besuppressed, thereby preventing the deterioration of the displaycharacteristics. Therefore, the active-matrix type liquid crystaldisplay device can be achieved with an improved yield at low cost withhigh reliability.

As another preferred form of the first or the second active-matrix typeliquid crystal display device, it may be arranged such that eachauxiliary line is formed in a width narrower than that of the signalline or the scanning line to be connected thereto.

The feature that the auxiliary line is formed narrower than the signalline or the scanning line offers an effect that the region where lightis blocked by the auxiliary lines in the pixel can be reduced, therebysuppressing a drop in aperture ratio of the pixel. Moreover, an increasein parasitic capacitance between the signal line or the scanning lineand the pixel electrode can be suppressed.

As a still another preferred form, the first or second active-matrixtype liquid crystal display device may be arranged such that eachauxiliary lines are made of a transparent electrically conductivematerial.

This feature offers an effect that the light that is transmitted throughthe pixel will not be blocked by the auxiliary lines, thereby preventinga drop in aperture ratio of the pixel. As a result, the active-matrixtype liquid crystal display having the described arrangement offers animproved display quality.

As a still another preferred form of the first or second active-matrixtype liquid crystal display device, it may be arranged such that thepixel electrodes is formed on an organic insulating film which coversthe signal electrode.

In general, as an organic insulating film has a low dielectric constant,a capacitance between the pixel electrode and the signal line can bereduced. Also, the capacitance between the scanning line formed underthe signal line and the pixel electrode can be reduced. Therefore, ageneration of crosstalk due to the capacitance formed between the pixelelectrode and the signal line can be suppressed, and also the pixelvoltage that is pulled-in due to the capacitance formed between thescanning line and the pixel electrode can be suppressed. Therefore, theactive-matrix type liquid crystal device permits an improved displayquality by suppressing the effect from each of the describedcapacitances.

As a still another preferred form of the first or second active-matrixtype liquid crystal display device, it may be arranged such that aninsulating film is formed between the pixel electrodes and the signallines or the scanning lines. On the other hand, two auxiliary lines arerespectively connected to two adjacent signal lines or two adjacentscanning lines which are disposed so as to surround the pixel electrode.According to the described arrangement, capacitances are respectivelyformed between the pixel electrode and one auxiliary line and betweenthe pixel electrode and the other auxiliary line, and the auxiliarylines are formed in such a manner that the described two capacitancesare equal. Further, a signal voltage whose polarity reverses per everyline is applied to the signal line.

For example, the auxiliary lines are disposed in such a manner thatportions connected to one signal line or scanning line are alternatelyformed between both sides of the signal line or the scanning line. Inother words, the auxiliary lines are disposed in such a manner that aplurality of the auxiliary lines are connected to one signal line orscanning line on its opposite sides every one auxiliary line.

In the arrangement where the signal lines are formed in the describedpattern, and a signal voltage whose polarity reverses per line isapplied to the signal lines, influences from respective capacitancesbetween the pixel electrode and the auxiliary lines can be cancelledout, thereby reducing an influence of the capacitance. As a result, theactive-matrix type liquid crystal display having the describedarrangement permits a display quality to be improved by reducing ageneration of crosstalk due to the capacitance.

The first method of compensating for a defective pixel in accordancewith the present invention for the first active-matrix type liquidcrystal display device is characterized in that the signal line is cutoff on both sides of the scanning line when a leakage defect occurred ata crossing point between the scanning line and the signal line.

According to the described method, when a leakage defect occurred in thecrossing point between the scanning line and the signal line, the signalline is disconnected on both sides of the scanning line. After thesignal line is disconnected, a voltage is not applied to the signal lineat the connecting portion, thereby preventing a generation of leakage.Moreover, even after the signal line is disconnected, as a voltage canbe kept applying to the signal line by the auxiliary lines, a generationof a defective pixel can be prevented. As a result, the method ofcompensating for a defective pixel electrode permits an improved signalquality by eliminating the leakage defect.

The second method of compensating for a defective pixel designed for thesecond active-matrix type liquid crystal display device is characterizedin that the scanning line is cut of f on both sides of the signal linewhen a leakage defect occurred at a crossing point between the signalline and the scanning line.

The described method offers the same effect as achieved by the firstmethod of compensating for a defective pixel electrode. That is, bycutting off the scanning line, a voltage is not applied to theconnecting portion of the scanning line, thereby preventing a generationof leakage. Moreover, even after the signal line is disconnected, as avoltage can be kept applying to the scanning line by the auxiliarylines, a generation of a defective pixel can be prevented. As a result,the method of compensating for a defective pixel electrode permits animproved signal quality by eliminating the leakage defect.

The novel features which are considered as characteristic of theinvention are set forth in particular in the appended claims. Theimproved treatment method, as well as the construction and mode ofoperation of the improved treatment apparatus, will, however, be bestunderstood upon perusal of the following detailed description of certainspecific embodiments when read in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing a structure of a wiring substrate for usein an active-matrix type liquid crystal display device in accordancewith the first embodiment of the present invention.

FIG. 2 is a plan view which shows an enlarged view of the arrangement ofone pixel region in the wiring substrate of FIG. 1.

FIG. 3 is a cross-sectional view of the wiring substrate of FIG. 2 takenalong lines A-A′.

FIG. 4 is a cross-sectional view showing the arrangement of a portion ofa TFT in the wiring substrate of FIG. 2.

FIG. 5 is a plan view showing another arrangement where an auxiliaryline is connected to the signal line in the wiring substrate inaccordance with the first embodiment of the present invention.

FIG. 6 is a plan view showing a still another arrangement where anauxiliary line is connected to the signal line in the wiring substratein accordance with the first embodiment of the present invention.

FIG. 7 is a plan view showing an arrangement of one pixel region of awiring substrate for use in an active-matrix type liquid crystal displaydevice in accordance with the second embodiment of the presentinvention.

FIG. 8 is a plan view showing another arrangement of one pixel region ofa wiring substrate for use in an active-matrix type liquid crystaldisplay device in accordance with the second embodiment of the presentinvention.

FIG. 9 is a plan view showing an arrangement of one pixel region of awiring substrate for use in an active-matrix type liquid crystal displaydevice in accordance with the third embodiment of the present invention.

FIG. 10(a) and FIG. 10(b) are waveform diagrams showing waveforms ofvoltage respectively applied to signal lines and scanning lines when asource line inversion or a dot inversion occurs in the wiring substrateshown in FIG. 9.

FIG. 11 is a plan view showing an arrangement of a wiring substrate foruse in an active-matrix type liquid crystal display device in accordancewith a fourth embodiment of the present invention.

FIG. 12 is a plan view showing the state where a disconnection defectoccurred in the wiring substrate of FIG. 11.

FIG. 13 is a plan view which explains a compensation for a leakagedefect generated in the wiring substrate of FIG. 11.

FIG. 14 is a plan view showing the arrangement of one pixel region of aconventional active-matrix type liquid crystal display device adopting adouble scanning line.

FIG. 15 is a plan view showing an arrangement of one pixel region of awiring substrate for use in a conventional active-matrix type liquidcrystal display device having an auxiliary capacitance of theCs-on-Common structure.

FIG. 16 is a cross-sectional view of the wiring substrate-of FIG. 15taken along lines B-B′.

FIG. 17 is a plan view showing another arrangement of one pixel regionof the conventional active-matrix type liquid crystal display devicehaving an auxiliary capacitance of the Cs-on-Common structure.

FIG. 18 is a plan view showing the arrangement of one pixel region ofthe conventional active-matrix type liquid crystal display device havingan auxiliary capacitance of the Cs-on-Gate structure.

FIG. 19 is a plan view showing another arrangement of one pixel regionof the wiring substrate of the conventional active matrix-type liquidcrystal display having an auxiliary capacitance of the Cs-on-Gatestructure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

The following descriptions will discuss one embodiment of the presentinvention in reference to FIG. 1 through FIG. 6.

As shown in FIG. 1, an active-matrix type liquid crystal display devicein accordance with the present embodiment (hereinafter referred to as aliquid crystal display device) is provided with a wiring substrate whichincludes a plurality of scanning lines 1, a plurality of signal lines 2,a plurality of auxiliary capacitance lines 3 (hereinafter referred to asCs lines), etc. The liquid crystal display device is provided with aliquid crystal panel including the described wiring substrate. Theliquid crystal panel is arranged such that the wiring substrate and acounter substrate whereon a common electrode (not shown) is disposed areconnected together with a predetermined interval between them. In thespace formed between the substrates, a liquid crystal is sealed.

The scanning lines 1 formed in parallel at predetermined intervals, thesignal lines 2 formed in parallel at predetermined intervals and the Cslines 3 formed in parallel at predetermined intervals are disposed on asubstrate 8 (see FIG. 3) to be described later. The signal lines 2 whichserve as signal lines are formed so as to cross the scanning lines 1which serve as scanning lines at right angle. The Cs lines 3 are used incommon among all the pixels, and are formed parallel to the scanninglines 1. In a region surrounded by the adjacent scanning lines 1 and theadjacent signal lines 2, provided is a pixel electrode 4.

Under the pixel electrode 4, formed are auxiliary lines 5. The auxiliarylines 5 are formed at a central portion of the pixel electrode 4 so asto be parallel to the signal lines 2. Each auxiliary line 5 forms a pairwith corresponding signal line 2 for each pixel electrode 4. Theauxiliary line 5 is made of a metallic material of the same kind as thatof the signal line 2 with a smaller width than that of the signal line2. Here, the auxiliary line 5 may be made of an electrically conductivefilm such as indium tin oxide (ITO).

In a vicinity of a crossing point between the scanning line 1 and thesignal line 2, provided is a TFT 6 which serves as a switching element.The TFT 6 includes a semiconductor layer 6 a. The semiconductor layer 6a is formed on the scanning line 1 via a gate insulating film 9 (FIG.3), to be described later. The ends of the semiconductor layer 6 a arerespectively connected to the signal line 2 and a drain electrode 7.Further, an intermediate portion of the semiconductor layer 6 a isformed as a channel region. The drain electrode 7 is pulled under thepixel electrode 4 so as to be connected therewith. Such connection ismade by a contact portion 4 a of the pixel electrode 4.

By applying an ON-voltage (scanning voltage) to the scanning line 1, theTFT 6 is switched ON, and further, a voltage that is to be applied tothe signal lines 2 is applied to the pixel electrode 4 so as to chargethe pixel capacitance.

The Cs lines 3 are formed in such a manner that each Cs line 3 isdisposed between adjacent two scanning lines 1. As shown in FIG. 2 andFIG. 3, the Cs line 3 is formed on the substrate 8 made of an insulatingand transparent material such as glass, etc. As shown in FIG. 3 and FIG.4, the scanning line 1 is formed in the same layer as the Cs line 3.

As shown in FIG. 3, on the Cs line 3, two auxiliary capacitanceelectrodes 10 (hereinafter referred to as Cs electrodes) are formed foreach pixel via the gate insulating film 9. On the gate insulating film9, auxiliary lines 5 are formed between the Cs electrodes 10, and lowerlayer signal lines 11 are formed on both sides of the Cs electrodes 10.On the lower layer signal lines 11, the signal lines 2 are formed.

Further, the described layers are covered with an insulating film 12whereon a pixel electrode 4 is formed. The pixel electrode 4 has concavecontact portions 4 b respectively in contact with the Cs electrodes 10.The insulating film 12 is made of an organic material of a lowdielectric constant represented by resin.

The Cs electrodes 10 are formed on the Cs lines 3 which are used incommon among all the pixels. The auxiliary capacitance has theCs-on-Common structure composed of the Cs line 3, the Cs electrodes 10and the gate insulating film 9 sandwiched therebetween.

It should be noted here that the present embodiment is not limited tothe described arrangement, and other arrangements, for example,below-explained arrangements may be adopted.

In the arrangement shown in FIG. 5, one of the Cs electrodes 10 isconnected to the drain electrode 7 through the connection line 13. Thisarrangement has the Cs-on-Common structure as in the arrangement of FIG.2, but is different from the arrangement of FIG. 2 in that the drainelectrode 7 is connected to the picture electrode 4 via the Cs electrode10.

On the other hand, in the arrangement shown in FIG. 6, a part of the Cselectrodes 10 is formed on the scanning line 1 for the adjacent pixelelectrode 4. This arrangement has the Cs on gate structure wherein anauxiliary capacitance is formed by the scanning line 1, the Cs electrode10 and the described gate insulating film 9 (see FIG. 3) sandwichedtherebetween.

The manufacturing process of the wiring substrate having the describedarrangement will be explained in reference to FIG. 3 and FIG. 4.

First, an electrically conductive thin film is formed on the insulatingand transparent substrate 8, and the scanning line 1 and the Cs line 3are formed by performing a patterning of the electrically conductivethin film. In this embodiment, a glass substrate is used for thesubstrate 8; however, a material for use in the substrate 8 is notlimited to glass, and any materials having an insulating property and aproperty that light is transmissible therethrough may be used. For theelectrically conductive thin film, a Ta series metallic material may beused; however, the material for the electrically conductive thin film isnot limited to the Ta series metallic material, and other electricallyconductive materials may be used.

Next, an insulating thin film (gate insulating film 9), a semiconductorthin film (semiconductor layer 6 a) and a semiconductor-electrodecontact material thin film are formed in this order so as to cover thescanning lines 1 and the Cs lines 3 to form semiconductor contact layers14.

Here, silicon nitride is used as the insulating thin film, amorphoussilicon is used as the semiconductor thin film, and n⁺ amorphous siliconis used as a contact material thin film. It should be noted here thatthe insulating thin film may be formed using other insulating materialsthan the silicon nitride.

Thereafter, the transparent electrically conductive thin film and theelectrically conductive thin film are formed so as to be superimposed,and a patterning of an electrically conductive thin film is performed,thereby forming the signal line 2, the drain electrode 7 and the sourceelectrode 15. Subsequently, by performing a patterning of thetransparent electrically conductive thin film, the lower layer signalline 11, the lower layer drain electrode 16, the lower layer sourceelectrode 17, the auxiliary lines 5, and the Cs electrode 10 are formed.Namely, the TFT 6 is formed by the described patterning. As to the TFT6, as long as it serves as a switching element, the material, thestructure and the manufacturing method thereof are not particularlylimited.

Here, ITO is used as the transparent electrically conductive thin film,and the Ta series metallic material is used as the electricallyconductive thin film. However, other electrically conductive materialsmay be used. Additionally, it is permitted to form the signal lines 2,the auxiliary lines 5, the drain electrodes 7 and the Cs electrodes 10by a metallic material of one kind, or by a transparent electricallyconductive material such as ITO. In this case, the need of the lowersignal lines 11 is eliminated.

No matter which materials are used respectively for the transparentelectrically conductive thin film and the electrically conductive thinfilm, the auxiliary lines 5 are formed together with the signal lines 2,the Cs electrodes 10, etc., which are needed in manufacturing the wiringsubstrate. Therefore, the number of processes does not increase byproviding the auxiliary lines 5 compared with the conventionalmanufacturing method of the display element in that an increase in thenumber of processes required for forming the auxiliary lines 5 can beprevented.

The width of the signal line 2 is set to around 8 μm in consideration ofelectric driving conditions. The width of the auxiliary line 5 is set toaround 4 μm in consideration of a processing precision of the ITO.

Further, the insulating layer which serves as the insulating film 12 isformed, and a contact hall (see FIG. 4) for connecting the pixelelectrode 4 and the drain electrode 7 and another contact hall (see FIG.3) for connecting the pixel electrode 4 and the Cs electrode 10 areformed thereon. Here, the insulating layer is made of a photoconductiveacrylic resin with a thickness of around 3.0 μm. The dielectric constantof the acrylic resin is set to 3.5. Here, for the insulating layer,organic materials other than the acrylic resin may be used as long asthe materials show the insulating property.

Then, by forming and subsequently patterning the ITO, the pixelelectrode 4 is formed. Here, the contact portions 4 a and 4 b are formedin the contact hall. For the pixel electrode 4, other electricallyconductive materials than ITO may be used.

The wiring substrate having the structure shown in FIG. 3 and FIG. 4 areformed in the described manner.

The matrix display element in accordance with the present embodimenthaving the described arrangement offers the following advantageouscharacteristics:

(1) Even when a disconnection of the signal line 2 occurs, anapplication of a voltage to the pixel electrode 4 can be ensured by theauxiliary lines 5, thereby preventing a generation of a line-shapeddefect due to the disconnection;

(2) When a leakage occurs in a portion where the scanning line 1 and thesignal line 2 are crossed, or a portion where the scanning line 1 andthe auxiliary line 5 are crossed, the signal line 2 or the auxiliaryline 5 is cut off on both sides of the crossing point by projectingthereto a laser beam, etc. As a result, a voltage will not be applied tothe signal line 2 or the auxiliary line 5 at the defective crossingpoint, thereby eliminating a generation of leakage;

(3) By arranging the auxiliary line 5 so as to have a narrower widththan that of the signal line 2, a reduction in the aperture ratio of thepixel can be suppressed. Moreover, by forming the auxiliary line 5 bythe transparent electrically conductive material such as ITO, the lighttransmitted through the pixel will not be blocked by the auxiliary lines5, thereby preventing a reduction in the aperture ratio of the pixel;and

(4) By adopting resin for the insulating film 12, the capacitance(parasitic capacitance) between the signal lines 2 and the pixelelectrode 4, and the capacitance between the auxiliary line 5 and thepixel electrode 4 can be made smaller. Here, the smaller is thedielectric constant of the resin and the thicker is the resin layer, thesmaller is the capacitance, and the crosstalk due to the capacitance canbe reduced.

Second Embodiment

The following descriptions will discuss the second embodiment of thepresent invention in reference to FIG. 7 and FIG. 8. Here, membershaving the same functions as those of the first embodiment will bedesignated by the same reference numerals, and thus the descriptionsthereof shall be omitted here.

A liquid crystal display device in accordance with the present inventionincludes a wiring substrate respectively having a structure shown inFIG. 7 or FIG. 8. In both arrangements shown in FIG. 7 and FIG. 8,scanning lines 1, signal lines 2, Cs lines 3 and picture electrodes 4are disposed in the same manner as the wiring substrate adopted in thefirst embodiment.

On the wiring substrate shown in FIG. 7, a Cs electrode 21 is depositedon the Cs lines 3 via a gate insulating film (not shown), to form anauxiliary capacitance of the Cs on Common structure. The Cs electrode 21is in contact with the pixel electrode 4 at a contact portion 4 c. Inthe wiring substrate of the present embodiment, auxiliary lines 22 areformed in replace of the auxiliary lines 5 (see FIG. 1) adopted in thefirst embodiment.

The auxiliary lines 22 are formed between the scanning line 1 formed ata lower portion of the pixel electrode 4 and the Cs line 3 so as to beparallel to the scanning line 1. Although not shown, the auxiliary lines22 are connected to the scanning line 1 for each pixel electrode 4. As aresult, the auxiliary lines 22 respectively make pair with the scanninglines 1. The auxiliary lines 22 are made the same metallic material asthe scanning lines 1 with a constant width narrower than that of thescanning lines 1. The auxiliary lines 22 may be made of a transparentelectrically conductive film such as indium tin oxide (ITO).

On the wiring substrate shown in FIG. 8, the Cs electrode 21 is formedon the scanning line 1 through the gate insulating film. As a result,the auxiliary capacitance of the Cs-on-Gate structure is formed. The Cselectrode 21 is in contact with the pixel electrode 4 at a contactportion 4 d.

Both of the described wiring substrates are manufactured in the samemanner as the wiring substrate adopted in the first embodiment exceptthat the process of forming the auxiliary lines 5 in the firstembodiment is replaced by the process of forming the auxiliary lines 22together with the scanning lines 1 and the Cs lines 3.

In this process, an electrically conductive thin film made of, forexample, Ta series metallic material is formed on the surface of thesubstrate. Then, by performing a patterning of the electricallyconductive thin film, the scanning lines 1, the Cs lines 3 and theauxiliary lines 22 are formed. The described process may be formed bysuperimposing the transparent electrically conductive thin film such asITO, etc., and the electrically conductive thin film on the substrate.Then, by performing a patterning of the electrically conductive thinfilm, the scanning lines 1 and the Cs lines 3 are formed. Thereafter, apatterning of the transparent electrically conductive thin film isperformed to form the auxiliary lines 22.

The matrix display element in accordance with the present embodimenthaving the described arrangement offers the following advantageouscharacteristics:

(1) Even when a disconnection of the scanning line 1 occurs, anapplication of a voltage to the pixel electrode 4 can be ensured by theauxiliary lines 22, thereby preventing a generation of a line-shapeddefect due to the disconnection;

(2) When a leakage occurs in a portion where the scanning line 1 and thesignal line 2 are crossed, or a portion where the signal line 2 and theauxiliary line 22 are crossed, the scanning line 1 or the auxiliary line5 is cut off on both sides of the crossing point by projecting thereto alaser beam, etc. As a result, a voltage will not be applied to thescanning line 1 or the auxiliary line 22 at the crossing point, therebyeliminating a generation of leakage;

(3) By arranging the auxiliary line 22 so as to have a narrower widththan that of the scanning line 1, a reduction in the aperture ratio of apixel can be suppressed. Moreover, by forming the auxiliary lines 22 bythe transparent electrically conductive material such as ITO, the lighttransmitted through the pixel will hot be blocked by the auxiliary lines22, thereby preventing a reduction in the aperture ratio of the pixel;and

(4) By adopting resin for the insulating film 12, the capacitancebetween the scanning lines 1 and the pixel electrode 4 and thecapacitance between the auxiliary lines 22 and the pixel electrode 4 canbe made smaller. Here, the smaller is the dielectric constant of theresin and the thicker is the resin layer, the smaller is thecapacitance, and an amount of the pixel voltage that is pulled in by thecapacitance can be reduced.

The pixel voltage is pulled in through the following mechanism: When acapacitance (C_(gd)) between the gate and the drain (pixel) increases,and afterward the gate is set ON so as to charge the pixel, and then thegate is set OFF. In this state, the drain potential is pulled-in to thegate through the capacitance (C_(gd)), and as a result, the potential ofthe pixel drops.

The electric potential thus pulled-in becomes a DC component to beapplied to the liquid crystal sealed between the pixel electrode and thecommon electrode. As this DC component adversely affects the liquidcrystal, the DC component is cancelled out by optimizing a voltage to beapplied to the common electrode. However, when the C_(gd) is large,variations in the capacitance C_(gd) are likely to increase due to thevariations in processing each pixel, and the DC component cannot becancelled out completely in the liquid crystal panel, thereby reducing areliability of the liquid crystal. In contrast, according to the wiringsubstrate of the present embodiment, as the capacitance C_(gd) can bemade smaller, a reliability of the liquid crystal can be improved.

Third Embodiment

The following descriptions will discuss the third embodiment of thepresent invention in reference to FIG. 9, FIG. 10(a) and FIG. 10(b).

As shown in FIG. 9, a liquid crystal display device in accordance withthe present embodiment is provided with a wiring substrate whereon twoadjoining auxiliary lines 31 and 32 are formed between adjoining signallines 2. The auxiliary lines 31 and 32 are made of a transparentelectrically conductive material such as a metallic material or ITO soas to have the same width, and are formed in parallel to the signallines 2 under the pixel electrode 4. For each pixel electrode 4, theauxiliary line 31 is connected to a signal line 2 for applying a voltageto the pixel electrode 4 in a line. The auxiliary line 32 is connectedto the signal line 2 for applying a voltage to the pixel electrode 4 ofthe adjacent line.

By the described arrangement of the auxiliary lines 31 and 32, three Cselectrodes 33 are formed on the Cs line 3 so as to avoid the auxiliarylines 31 and 32.

The manufacturing method of the described wiring substrate of thepresent embodiment differs from that of the first embodiment in itsrespective patterning processes for forming the auxiliary lines and theCs electrode and a patterning process of the insulating layer forforming a contact hall.

Specifically, the wiring substrate of the present embodiment is arrangedsuch that the capacitance between the pixel electrode 4 and theauxiliary line 31 is set equal to the capacitance between the pixelelectrode 4 and the auxiliary line 32. When displaying in the liquidcrystal display device provided with the described wiring substrate, apolarity of the voltage to be applied to the signal line 2 reverses atevery line. For example, when carrying out a source line inversion, thewaveform (sources 1 and 2) shown in FIG. 10(a) is applied to the twosignal lines 2 which are adjacent to each other. On the other hand, whenperforming a dot inversion in which the line inversion and 1H inversionare combined, the waveform (sources 1 and 2) shown in FIG. 10(b) isapplied to the signal lines 2 which are adjacent to each other.

For certain pixel electrode 4, supposed the capacitance of pixel, thecapacitance between the pixel electrode 4 and the signal line 2(auxiliary line 5), and the capacitance between the pixel electrode 4and the next signal line 2 (auxiliary line 5) be respectively C_(1c)(liquid crystal capacitance)+C_(cs) (auxiliary capacity C_(cs)), C_(sd1)and C_(sd2), and respective changes in potential in the signal line 2and the next signal line 2 be V_(s1) and V_(s2). Then, the effect on thepixel potential V_(d) by the capacitance C_(sd) can be approximated bythe following formula:

ΔV _(d) =V _(s1) ×C _(sd1)/(C _(sd1) +C _(1c) +C _(cs))+V _(s2) ×C_(sd2)/(C _(sd2) +C _(1c) +C _(cs)).

In the line inversion or the dot inversion, as the respective potentialsV_(s1) and V_(s2) have opposite polarities (line sources 1 and 2 in FIG.10(a) and FIG. 10(b)), ΔV_(d), a change in pixel potential, can be madesmaller. Namely, as C_(sd1) is equal to C_(sd2), the above-mentionedformula can be rewritten as follows, and the ΔV_(d) can be mostefficiently reduced.

ΔV _(d)=(V _(s1) +V _(s2))×C _(sd)/(C _(sd) +C _(1c) +C _(cs)),

wherein C_(sd1) (=C_(sd2)) is denoted by C_(sd).

The described features of the present embodiment permits the effect fromthe capacitance to be reduced, thereby providing a liquid crystaldisplay of high display quality by suppressing a generation ofcrosstalk. Here, the crosstalk suggests a crosstalk generated in thedirection of the signal line 2.

Fourth Embodiment

The following descriptions will discuss the fourth embodiment of thepresent invention in reference to FIG. 11 through FIG. 13.

As shown in FIG. 11, a liquid crystal display device in accordance withthe present embodiment has a wiring substrate whereon a plurality ofauxiliary lines 41 are formed under pixel electrodes 4. For example, theauxiliary lines 41 are disposed in such a manner that portions connectedto one signal line 2 or scanning line 1 are alternately formed betweenboth sides of the signal line 2 or the scanning line 1. In other words,the auxiliary lines are disposed in such a manner that a plurality ofthe auxiliary lines 41 are connected to one signal line 2 or scanningline 1 on its opposite sides every one auxiliary line 41. Between thepixel electrodes 4 which are adjacent to each other along the scanninglines 1, one end of the two auxiliary lines 41 is connected to thesignal line 2 at the closest position.

By the described arrangement of the auxiliary lines 41, for each pixelelectrode 4, two Cs electrodes 10 are formed on the Cs line 3 so as toavoid the auxiliary lines 41.

As in the case of the third embodiment, the manufacturing method of thewiring substrate in accordance with the present embodiment differs fromthat of the first embodiment in respective patterning processes forforming the auxiliary lines and the Cs electrode and the patterningprocess of the insulating layer for forming a contact hall.

The wiring substrate of the present embodiment is arranged such therespective capacitances between the pixel electrode 4 and two auxiliarylines 41 formed under the pixel electrode 4 are equal. When displayingin the liquid crystal display device having the described wiringsubstrate, the polarity of the voltage to be applied to the signal line2 reverses at every line as described earlier. As a result, the effectsfrom the capacitance can be reduced, thereby providing a high qualityliquid crystal display which hardly generates a crosstalk.

Furthermore, as the wiring substrate of the present embodiment isarranged such that the auxiliary lines 41 are dispersed along the signalline 2, a washing defect hardly occurs in the processes using someliquid such as wet etching, washing, etc., to be performed in themanufacturing process of the wiring substrate. Therefore, compared withthe wiring substrate where the auxiliary lines 31 and 32 are formedsuccessively along the signal line (see FIG. 9), the wiring substrate ofan improved quality can be achieved.

Furthermore, the arrangement of the present invention offersadvantageous characteristics over the arrangement of the thirdembodiment in that the number of the portions where the auxiliary lines41 cross the scanning lines 1 and the Cs lines 3 can be reduced, therebysuppressing a generation of a leakage defect at the crossing point.

When a disconnection defect occurred in the wiring substrate, as shownin FIG. 12, a voltage is applied to the signal line 2.

For example, when the signal line 2 (2A) is disconnected at adisconnected portion P, the voltage is applied to the adjacent signalline 2A by making a circuit around the disconnected portion P throughthe auxiliary lines 41 (41A).

In the pixel electrode 4, when the signal line 2 (2B) and the auxiliarylines 41 (41B) connected to the adjacent signal line 2A are disconnectedat a disconnected portion Q, the voltage takes the disconnected portionQ around by the auxiliary line 41 (41C) to be applied to the signal line2B.

In the wiring substrate, when a leakage is generated, as shown in FIG.13, the line-shaped defect is purposely disconnected using a laser beamto compensate for the leakage. In the present embodiment, a YAG(Yttrium-Aluminum-Garnet) laser with a laser power of from 10⁻⁹ to 10⁻⁶J/μm² is used in the state where the wiring substrate permits alightening display.

Here, the lightening display permitting state indicates the state wherea liquid crystal panel is assembled by laminating the wiring substrateand the counter substrate and sealing the liquid crystal therebetween. Asignal of a simple waveform is applied to the scanning lines 1 and thesignal line 2 of the described liquid crystal panel to observe theleakage between the scanning line 1 and the signal line 2.

For example, in the case where a leakage occurred in a crossing point Rbetween the scanning line 1 and the signal line 2, the signal line 2 iscut off by projecting the laser beam on both sides (cut portions R₁ andR₂) of the scanning line 1.

Similarly, when a leakage defect occurred in a crossing point S betweenthe signal line 2 and the Cs line 3, the signal line 2 is cut off byprojecting a laser beam on both sides of the Cs line 3 (cut portions S₁and S₂).

Furthermore, when a leakage occurs at the crossing point T between thescanning line 1 and the auxiliary line 41, the auxiliary line 41 is cutoff by projecting a laser beam on both sides of the scanning line 1 (cutportions T₁ and T₂).

In the described preferred embodiment, explanations have been giventhrough the case where a wire is disconnected by projecting thereto alaser beam. However, the present invention is not limited to the methodadopted in this preferred arrangement. For example, when a generation ofa leakage in the wiring substrate is observed before being laminated tothe counter substrate, the disconnection using the physical or chemicalmeans other than the laser beam may be adopted to compensate for theleakage. The same can be said for compensation in the manufacturingprocess of the wiring substrate.

As described, by forming the auxiliary line 41, even if a disconnectiondefect occurs, the voltage can be kept applying to the signal line 2.Furthermore, even if a leakage defect occurs, it is permitted topurposely disconnect to eliminate the leakage defect. As described, evenif the disconnection is made purposely, as the double-wire is provided,the voltage can be kept applying to the signal line 2 as in the case ofthe disconnection defect.

The described technique of compensating for the disconnection defect andthe leakage defect can be also adopted to the respective wiringsubstrates adopted in the aforementioned preferred embodiments.

Furthermore, in the respective wiring substrates of the describedpreferred embodiments and the present embodiment, the TFT 6 of thereverse-stagger type is adopted. However, the present invention is alsoapplicable to the case where the TFT of the stagger-type or MIM elementis adopted as the switching element.

In the case where the TFT of the stagger type is adopted, the respectivepositions of gate and the semiconductor layer would differ from the casewhere the reverse-stagger type TFT is adopted.

In the case of adopting the MIM element, the scanning line 1 is omittedfrom the described wiring substrate, and the scanning line of the samewidth as that of the pixel electrode is formed on the counter substrate(color filter substrate) in replace of the described scanning line 1.Therefore, in this case, the present invention can be applied to thesignal line formed together with the MIM element on the wiringsubstrate.

In this case, however, the pixel electrode is required to be formed on adifferent layer from the signal line via the insulating film asdescribed in each of the preferred embodiments.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic and specific aspects of the instantcontribution to the art and, therefore, such adaptations should and areintended to be comprehended within the meaning and range of equivalenceof the appended claims.

What is claimed is:
 1. The active-matrix type liquid crystal displaydevice comprising: a substrate; pixel electrodes disposed in a matrixform on said substrate; a plurality of scanning lines in a layer of saidsubstrate, for applying a scanning line voltage to each pixel electrode,said plurality of scanning lines being aligned in parallel so as to passbetween pixel electrodes; a plurality of signal lines crossing saidplurality of scanning lines at a right angle, said signal lines applyinga signal voltage to each pixel electrode, and said plurality of signallines being aligned in parallel so as to pass between pixel electrodes;each pixel electrode is disposed in a region adjacent scanning lines andadjacent signal lines; a switching element for switching ON/OFF anapplication of a signal voltage to each pixel electrode through eachsignal line by a scanning voltage to be applied to each scanning line,and auxiliary lines formed in the same layer as said scanning lines,each auxiliary line short-circuiting two regions of one of saidplurality of scanning lines and applying the scanning voltagerespectively to two pixel electrodes which are adjacent to each otheralong the scanning line.
 2. An active-matrix type liquid crystal displaydevice, comprising; a substrate; a plurality of scanning lines formed onsaid substrate; a plurality of signal lines formed so as to cross saidplurality of scanning lines at right angles; pixel electrodes eachdisposed in a region adjacent scanning lines and adjacent signal lines;and switching elements for switching ON/OFF application of signalvoltages to said pixel electrodes through said plurality of signal linesby means of scanning voltages to be applied to said plurality ofscanning lines, wherein: said plurality of signal lines includesauxiliary lines formed in a same layer as said plurality of signal linesand electrically connected to said plurality of signal lines; said pixelelectrodes are insulated from said plurality of signal lines and saidauxiliary lines to form a separate layer, and each of said pixelelectrodes has a first overlapping portion which overlaps at least oneof a first signal line and an auxiliary line which short-circuits thefirst signal line, each of said pixel electrodes has a secondoverlapping portion which overlaps at least one of a second signal line,and an auxiliary line which short-circuits the second signal line; andthe two overlapping portions have equal capacitances.
 3. Theactive-matrix type liquid crystal display device as set forth in claim 2wherein: a signal voltage whose polarity reverses at every signal lineis applied to each signal line; and a voltage applied to one of the twooverlapping portions has an opposite polarity from that applied toanother of the overlapping portions.
 4. A method of compensating for adefective pixel designed for an active-matrix type liquid crystaldisplay device including: a substrate; a plurality of scanning linesformed on said substrate; a plurality of signal lines formed so as tocross said plurality of scanning lines at right angles; pixel electrodeseach disposed in a region adjacent scanning lines and adjacent signallines; and switching elements for switching ON/OFF application of signalvoltages to said pixel electrodes through said plurality of signal linesby means of scanning voltages to be applied to said plurality ofscanning lines, wherein said plurality of signal lines includesauxiliary lines formed in a same layer as said plurality of signal linesand electrically connected to said plurality of signal lines; said pixelelectrodes are insulated from said plurality of signal lines and saidauxiliary lines to form a separate layer, and each of said pixelelectrodes has a first overlapping portion which overlaps at least oneof a first signal line and an auxiliary line, which short-circuits thefirst signal line, each of said pixel electrodes has a secondoverlapping portion which overlaps at least one of a second signal line,and an auxiliary line which short-circuits the second signal line; andthe two overlapping portions have equal capacitances, wherein: saidmethod is such that when a leakage defect occurs at a crossing pointbetween a scanning line and a signal line, the signal line is cut off onboth sides of the scanning line.
 5. An active-matrix type liquid crystaldisplay device, comprising a substrate; a plurality of scanning linesformed on said substrate; a plurality of signal lines formed so as tocross said plurality of scanning lines at right angles; pixel electrodeseach disposed in a region adjacent scanning lines and adjacent signallines; switching elements for switching ON/OFF application of signalvoltages to said pixel electrodes through said plurality of signal linesby means of scanning voltages to be applied to said plurality ofscanning lines, wherein: said plurality of signal lines includesauxiliary lines formed in a same layer as said plurality of signal linesand electrically connected to said plurality of signal lines; said pixelelectrodes are insulated from said plurality of signal lines and saidauxiliary lines to form a separate layer, and each of said pixelelectrodes has a first overlapping portion which overlaps at least oneof a first signal line and an auxiliary line which short-circuits thefirst signal line, each of said pixel electrodes has a secondoverlapping portion which overlaps at least one of a second signal lineand an auxiliary line which short-circuits the second signal line; and avoltage applied to one of the two overlapping portions has an oppositepolarity from that applied to another of the overlapping portion.
 6. Amethod of compensating for a defective pixel designed for anactive-matrix type liquid crystal display device including: a substrate;a plurality of scanning lines formed on said substrate; a plurality ofsignal lines formed so as to cross said plurality of scanning lines atright angles; pixel electrodes each disposed in a region adjacentscanning lines and adjacent signal lines; and switching elements forswitching ON/OFF application of signal voltages to said pixel electrodesthrough said plurality of signal lines by means of scanning voltages tobe applied to said plurality of scanning lines, wherein: said pluralityof signal lines includes auxiliary lines formed in a same layer as saidplurality of signal lines and electrically connected to said pluralityof signal lines; said pixel electrodes are insulated from said pluralityof signal lines and said auxiliary lines to form a separate layer, andeach of said pixel electrodes has a first overlapping portion whichoverlaps at least one of a first signal line and an auxiliary line whichshort-circuits the first signal line, each of said pixel electrodes hasa second overlapping portion overlaps at least one of a second signalline and an auxiliary line which short-circuits the second signal line;and a signal voltage whose polarity reverses at every signal line whenapplied to each signal line, and a voltage applied to one of the twooverlapping portions has an opposite polarity from that applied toanother of the overlapping portions, wherein: said method is such thatwhen a leakage defect occurs at a crossing point between a scanning lineand a signal line, the signal line is cut off on both sides of thescanning line.